The present invention relates to gaseous-discharge lamps, and more particularly to such a lamp having a reflector in the interior thereof.
A conventional gaseous-discharge lamp has an arrangement as shown in FIGS. 1 and 2. As shown therein, a glass-made valve 2 of a circular cross-section serves as an enclosure in which an inert gas is hermetically confined. A light projection window 1 is formed on the top face of the enclosure from which light is emitted. A glass stem 3 is provided in the bottom of the valve 2, which includes a circular glass plate 3a and lead wires 4a, 4b, 4c, 4d passing through the glass plate 3a and extending to the interior of the valve 2. These lead wires are hermetically sealed and fixedly supported by beads 3b. The beads 3b are integrally formed in the glass plate 3a and arranged radially symmetrically in coaxial relation with the circular cross-section of valve 2. In the interior of the valve 2, a cathode 5, an anode 6, a trigger probe electrode 7 and a sparker electrode 8 are disposed which are connected to the lead wires 4a, 4b, 4c and 4d, respectively. The cathode 5 and the anode 6 are parallel to the light projection window 1 and are disposed in confrontation with each other with a space therebetween. The tip end of the trigger probe electrode 7 is placed between the cathode 5 and the anode 6. The sparker electrode 8 is disposed at a lower position with respect to the cathode 5, the anode 6, and the trigger probe electrode 7. The sparker electrode 8 is surrounded by a ceramic sleeve so that the tip end of the electrode 8 projects therefrom. The outer periphery of the ceramic sleeve is further surrounded by a nickel sleeve 15 which is connected to the cathode lead wire 4a with a lead wire 16.
In operation, by the application of a predetermined voltage between the cathode 5 and the anode 6 and first and second trigger voltages to the trigger probe electrode 7 and the sparker electrode 8, respectively, a discharge first occurs between the sparker electrode 8 and the nickel sleeve 15, thereby emitting ultraviolet radiation. The ultraviolet rays emitted toward the space between the cathode 5 and the anode 6, causes a gaseous arc discharge occurs between the trigger probe electrode 7 and the cathode 5. The main discharge which produces the light then occurs between the cathode 5 and the anode 6.
Such a lamp has been extensively used as a stroboscopic light source, liquid chromatographic light source, spectrophotometric light source, photo-exciting light source, etc., because the light emitted ranges from ultraviolet to visible or near infrared. When the lamp is so used, it is required that a high intensity light be stably emitted from the lamp.
However, the conventional lamp per se is incapable of complying with such a requirement. It has therefore been a conventional practice to use a focusing lens or a cup-shaped reflection mirror in conjunction with the lamp for increasing the intensity of the light. The lens is positioned ahead of the light projection window to focus the light therefrom. The reflection mirror is attached to the rear of the lamp to surround the same so that the light directed backwardly is reflected from the reflection mirror. The use of the lens is inconvenient in that only a particular size of the lens is usable. The use of the reflection mirror is not efficient because of the large diameter access hole needed for receiving the lamp.